980
FXUS63 KLOT 120014
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
714 PM CDT TUE AUG 11 2026
KEY MESSAGES
- AFTERNOON SHOWERS/STORMS EXPECTED TO WANE INTO THIS EVENING.
- ANOTHER ROUND OF SHOWERS/STORMS POSSIBLE TONIGHT (30-50%),
INCLUDING THE POTENTIAL FOR SEVERE STORMS AND HEAVY RAINFALL.
- ADDITIONAL STRONG/SEVERE STORMS POSSIBLE WEDNESDAY.
DISCUSSION
ISSUED AT 310 PM CDT TUE AUG 11 2026
ONGOING SCATTERED SHOWERS AND STORMS WILL LINGER THIS AFTERNOON
AND EARLY EVENING IN THE WAKE OF SIGNIFICANT SEVERE WEATHER
EARLIER TODAY. THIS ACTIVITY IS EXPECTED TO WANE OVER THE NEXT
SEVERAL HOURS WITH CONVECTIVE INHIBITION/SUBSIDENCE IN PLACE
ACROSS THE CWA AS THE REINFORCED SURFACE BOUNDARY HAS PUSHED SOUTH
OF THE AREA ACROSS CENTRAL ILLINOIS.
WHILE THIS WILL LIKELY LEAD TO A LULL IN SHOWER/STORM CHANCES THIS
EVENING, ADDITIONAL THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
OVERNIGHT TONIGHT -- PRIMARILY ACROSS NORTHEAST ILLINOIS/NORTHWEST
INDIANA, INCLUDING THE CHICAGO AREA. THE AFOREMENTIONED BOUNDARY
IS EXPECTED TO WORK BACK NORTH ACROSS THE AREA WITH TIME THIS
EVENING WITH SHOWERS/STORMS POSSIBLY TRAINING ALONG/NORTH OF SAID
BOUNDARY. STRONG BUOYANCY ALOFT ON THE ORDER OF 3,500+ MUCAPE
COMBINED WITH DEEP-LAYER SHEAR ~35 KTS WILL SUPPORT A CONTINUED
THREAT FOR STRONG/SEVERE STORMS TONIGHT. GIVEN ANTICIPATED
CONVECTIVE EVOLUTION/TRAINING OF STORMS, PERHAPS OF EQUAL CONCERN
WILL BE THE POTENTIAL FOR HEAVY RAINFALL/FLOODING LATER TONIGHT.
STORMS IN AN ENVIRONMENT CHARACTERIZED BY ~2" PWATS WOULD LEAD TO
VERY EFFICIENT RAINFALL, AND POTENTIALLY BRING AN ADDITIONAL 1-2"+
OF RAIN TO AREAS THAT ALREADY SAW HEAVY RAINFALL EARLIER IN THE
DAY. WHILE UNCERTAINTY REMAINS RELATIVELY HIGH AT THIS TIME
(20-30% POPS TONIGHT), ANOTHER ROUND OF IMPACTFUL STORMS REMAINS
POSSIBLE TONIGHT.
THE AFOREMENTIONED BOUNDARY IS EXPECTED TO REMAIN DRAPED ACROSS
THE AREA DURING THE DAY WEDNESDAY WITH AMPLE INSTABILITY IN PLACE
ALONG AND TO ITS SOUTH, SUPPORTING CONTINUED THUNDERSTORM CHANCES
WEDNESDAY MORNING INTO WEDNESDAY EVENING. DAMAGING WINDS WILL BE
THE PRIMARY THREAT WITH STRONGEST STORMS, ESPECIALLY IF ANOTHER
LINE ORGANIZES AND TRACKS FROM NORTHWEST TO SOUTHEAST ACROSS THE
WARM SECTOR SOUTH OF THE FRONT DURING THE DAY. HAIL AND LOCALLY
HEAVY RAINFALL WILL ALSO BE POSSIBLE.
PRECISE DETAILS IN REGARDS TO TIMING AND IMPACTS BECOMES MORE
OBSCURE BEYOND WEDNESDAY, BUT ADDITIONAL ROUNDS OF THUNDERSTORMS
WILL BE POSSIBLE INTO THE END OF THE WEEK AS THE BOUNDARY LINGERS
ACROSS THE AREA AND KEEPS A WARM, MOIST AIRMASS IN PLACE WITH
RELATIVELY STRONG NORTHWEST FLOW ALOFT. A MORE SUBSTANTIAL BREAK
IN STORM CHANCES MAY NOT COME UNTIL LATE THIS UPCOMING WEEKEND OR
EARLY NEXT WEEK AS SURFACE HIGH PRESSURE MAY SETTLE MORE FIRMLY
OVER THE MIDWEST.
CORNISH
AVIATION /00Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 714 PM CDT TUE AUG 11 2026
FORECAST CONCERNS INCLUDE...
CHANCE OF THUNDERSTORMS TONIGHT AND AGAIN WEDNESDAY.
IFR/LIFR CIGS OVERNIGHT INTO WEDNESDAY MORNING.
POSSIBLE FOG OVERNIGHT INTO WEDNESDAY MORNING.
ISOLATED THUNDERSTORMS EXTEND FROM IKK TO DNV EARLY THIS EVENING
AND WILL CONTINUE MOVING SOUTHEAST AND AWAY FROM THE TERMINALS.
FOCUS IS ON A WAVE MOVING ACROSS NORTHERN IA AND SOUTHERN MN
WHERE CONVECTION IS SLOWLY STARTING TO DEVELOP. WHILE THERE
REMAINS UNCERTAINTY, THIS ACTIVITY MAY CONTINUE TO DEVELOP AND
SPREAD SOUTHEAST ACROSS NORTHERN IL LATER THIS EVENING AND THEN
CONTINUE INTO THE OVERNIGHT HOURS. LOW CONFIDENCE FOR COVERAGE
AND LOCATION BUT GIVEN CURRENT TRENDS, THUNDER MENTION IS NEEDED
FOR THIS TIME PERIOD, ROUGHLY 04Z-10Z. HOW THIS CONVECTION
EVOLVES AND DEVELOPS WILL PLAY A LARGE ROLE IN FOR ANY POSSIBLE
CONVECTION WEDNESDAY. THERE IS ANOTHER WAVE ACROSS THE DAKOTAS
THAT IS EXPECTED TO MOVE ACROSS THE AREA WEDNESDAY LATE MORNING
INTO THE AFTERNOON. IF CONVECTION OVERNIGHT IS WIDESPREAD
ENOUGH, ADDITIONAL CONVECTION WEDNESDAY MAY BE PUSHED SOUTH OF
THE TERMINALS. IN ADDITION, A LAKE BREEZE IS EXPECTED WEDNESDAY
AFTERNOON AND THAT BY ITSELF MAY ALLOW FOR AT LEAST ISOLATED
THUNDERSTORMS FOR THE CHICAGO TERMINALS. HOWEVER, CONFIDENCE IS
VERY LOW FOR THUNDERSTORM POTENTIAL WEDNESDAY AND AT THIS TIME,
HAVE OPTED TO STAY DRY AND ALLOW TRENDS TO EMERGE OVERNIGHT.
THE MODELS ARE SHOWING BOTH IFR/LIFR CIGS AND FOG DEVELOPING
OVERNIGHT AND PERSISTING INTO WEDNESDAY MORNING WITH THE LOWEST
VISIBILITIES LIKELY ACROSS NORTHWEST AND NORTHERN IL. ANY
REMAINING ONGOING PRECIPITATION MAY LIMIT HOW LOW VISIBILITIES
DROP. IN ADDITION, EXPECTED IFR/LIFR CIGS MAY ALSO LIMIT
VISIBILITIES. BUT GIVEN CURRENT TRENDS, HAVE CONTINUED IFR/LIFR
MENTION WITH THIS FORECAST.
SOUTHERLY WINDS THIS EVENING ARE EXPECTED TO BECOME MAINLY LIGHT
AND VARIABLE OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT WEST/
SOUTHWEST WINDS WEDNESDAY MORNING, THOUGH CONFIDENCE IS LOW. A
LAKE BREEZE IS EXPECTED WEDNESDAY FOR THE CHICAGO TERMINALS,
SHIFTING WINDS EASTERLY. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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